Semiconductor memory device

ABSTRACT

Provided herein is a semiconductor memory device including a memory cell array including a drain select transistor and a plurality of memory cells, a voltage generator configured to apply a program voltage, first and second pass voltages, and a drain control voltage to the memory cell array, a control logic configured to control the voltage generator so that during a program operation, after the program voltage is applied to a selected one of the plurality of memory cells, the program voltage applied to the selected memory cell is discharged while the first pass voltage or the second pass voltage is applied to memory cells adjacent to the selected memory cell.

CROSS-REFERENCE TO RELATED APPLICATION

The present application claims priority to Korean patent applicationnumber 10-2015-0136168 filed on Sep. 25, 2015 the entire disclosure ofwhich is incorporated herein in its entirety by reference.

BACKGROUND

1. Technical Field

Various embodiments of the present disclosure generally relate to anelectronic device, and more particularly, to a semiconductor memorydevice.

2. Related Art

Semiconductor devices, in particular, semiconductor memory devices maybe classified into volatile memory devices and nonvolatile memorydevices.

The nonvolatile memory device can maintain data stored therein even whenpower is turned off, although read and write speeds are comparativelylow. Therefore, the nonvolatile memory device is used when there is theneed for storing data which must be maintained regardless of supply ofpower. Representative examples of the nonvolatile memory device includeread-only memory (ROM), mask ROM (MROM), programmable ROM (PROM),erasable programmable ROM (EPROM), electrically erasable programmableROM (EEPROM), flash memory, phase-change random access memory (PRAM),magnetic RAM (MRAM), resistive RAM (RRAM), ferroelectric RAM (FRAM),etc. Flash memory may be classified into NOR type and NAND type memory.

The flash memory has both advantages of RAM in which data isprogrammable and erasable and advantages of ROM in which data storedtherein can be retained even when power is interrupted. Such flashmemory is widely used as a storage medium of portable electronic devicessuch as a digital camera, a personal digital assistant (PDA) and MP3.

The flash memory may be classified into a two-dimensional semiconductordevice in which strings are horizontally formed on a semiconductorsubstrate, and a three-dimensional semiconductor device in which stringsare vertically formed on a semiconductor substrate.

Three-dimensional semiconductor devices are memory devices which aredevised to overcome the limitation in the degree of integration oftwo-dimensional semiconductor devices and include a plurality of stringswhich are vertically formed on a semiconductor substrate. Each stringincludes a drain select transistor, which is coupled in series between abit line and a source line, a plurality of memory cells, and a sourceselect transistor.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram illustrating a representation of an example ofa semiconductor memory device according to the present disclosure.

FIG. 2 is a block diagram illustrating a representation of an example ofan embodiment of a memory cell array of FIG. 1.

FIG. 3 is a three-dimensional view illustrating a representation of anexample of a memory string included in a memory block according to thepresent disclosure.

FIG. 4 is a circuit diagram illustrating a representation of an exampleof the memory string illustrated in FIG. 3.

FIG. 5 is a flowchart illustrating a representation of an example of theoperation of the semiconductor memory device according to an embodimentof the present disclosure.

FIG. 6 is a waveform diagram representation of examples of signalsapplied to the memory cell array when the semiconductor memory device isoperated according to an embodiment of the present disclosure.

FIGS. 7A to 7D are diagrams illustrating representations of examples ofthe movement of electric charges trapped in a memory layer of a memorycell during a program operation of the semiconductor memory deviceaccording to an embodiment of the present disclosure.

FIG. 8 is a flowchart illustrating a representation of an example of theoperation of a semiconductor memory device according to an embodiment ofthe present disclosure.

FIG. 9 is a waveform diagram representation of examples of signalsapplied to the memory cell array when the semiconductor memory device isoperated according to an embodiment of the present disclosure.

FIGS. 10A to 10D are diagrams illustrating representations of examplesof the movement of electric charges trapped in a memory layer of amemory cell during a program operation of the semiconductor memorydevice according to an embodiment of the present disclosure.

FIG. 11 is a flowchart illustrating a representation of an example ofthe operation of a semiconductor memory device according to anembodiment of the present disclosure.

FIGS. 12A and 12B are waveform diagram representations of examples ofsignals applied to a memory cell array when the semiconductor memorydevice is operated according to an embodiment of the present disclosure.

FIGS. 13A to 13D are diagrams illustrating representations of examplesof the movement of electric charges trapped in a memory layer of amemory cell during the operation of the semiconductor memory deviceaccording to an embodiment of the present disclosure.

FIG. 14 is a flowchart illustrating a representation of an example ofthe operation of a semiconductor memory device according to anembodiment of the present disclosure.

FIG. 15 is a waveform diagram representation of examples of signalsapplied to a memory cell array when the semiconductor memory device isoperated according to an embodiment of the present disclosure.

FIGS. 16A to 16D are diagrams illustrating representations of examplesof the movement of electric charges trapped in a memory layer of amemory cell during a program operation of the semiconductor memorydevice according to an embodiment of the present disclosure.

FIG. 17 is a block diagram illustrating a representation of an exampleof a memory system including the semiconductor memory device of FIG. 1.

FIG. 18 is a block diagram illustrating a representation of an exampleof an application example of the memory system of FIG. 17.

FIG. 19 is a block diagram illustrating a representation of an exampleof a computing system including the memory system illustrated withreference to FIG. 18.

DETAILED DESCRIPTION

Advantages and features of the present disclosure, and methods forachieving the same will be discussed with reference to examples ofembodiments described later together with the accompanying drawings.Accordingly, the present disclosure is not limited to the followingembodiments and may be embodied in other types. Rather, theseembodiments are provided so that the present disclosure will bethorough, and complete, and will fully convey the technical spirit ofthe disclosure to those skilled in the art.

It will be understood that when an element is referred to as being“coupled” or “connected” to another element, it can be directly coupledor connected to the other element or intervening elements may be presenttherebteween. In the specification, when an element is referred to as“comprising” or “including” a component, it does not preclude anothercomponent but may further include other components unless the contextclearly indicates otherwise.

In the drawing figures, dimensions may be exaggerated for clarity ofillustration. It will be understood that when an element is referred toas being “between” two elements, it can be the only element between thetwo elements, or one or more intervening elements may also be present.Like reference numerals refer to like elements throughout.

Various embodiments of the present disclosure may be directed to asemiconductor memory device or method thereof which can mitigatevariation in threshold voltage due to retention deteriorationcharacteristics during a program operation.

An embodiment of the present disclosure may provide a semiconductormemory device. The semiconductor memory device may include a memory cellarray including a drain select transistor and a plurality of memorycells. The semiconductor memory device may include a voltage generatorconfigured to apply a program voltage, first and second pass voltages,and a drain control voltage to the memory cell array. The semiconductormemory device may include a control logic configured to control thevoltage generator so that during a program operation, after the programvoltage is applied to a selected one of the plurality of memory cells,the program voltage applied to the selected memory cell is dischargedwhile the first pass voltage or the second pass voltage is applied tomemory cells adjacent to the selected memory cell.

An embodiment of the present disclosure may provide a semiconductormemory device. The semiconductor memory device may include a memory cellarray including a plurality of memory cells and a drain selecttransistor. The semiconductor memory device may include a voltagegenerator configured to apply a program voltage or a pass voltage toword lines of the memory cell array. The semiconductor memory device mayinclude a control logic configured to control the voltage generator sothat before a program operation, the pass voltage is applied to odd onesof the word lines while the program voltage is applied to even ones ofthe word lines, and then the program voltage is applied to the odd wordlines while a potential of the even word lines is discharged.

An embodiment of the present disclosure may provide a semiconductormemory device. The semiconductor memory device may include a memory cellarray including a plurality of memory cells and a drain selecttransistor. The semiconductor memory device may include a voltagegenerator configured to apply a program voltage or a pass voltage toword lines of the memory cell array. The semiconductor memory device mayinclude a control logic configured to control the voltage generator sothat after the program voltage is applied to the word lines before aprogram operation, a potential of even ones of the word lines and apotential of odd ones of the word lines are alternately discharged.

FIG. 1 is a block diagram illustrating a representation of an example ofa semiconductor memory device according to the present disclosure.

Referring to FIG. 1, a semiconductor memory device 100 may include amemory cell array 110, an address decoder 120, a read-and-write circuit130, a control logic 140, and a voltage generator 150.

The memory cell array 110 may include a plurality of memory blocks BLK1to BLKz. The memory blocks BLK1 to BLKz are coupled to the addressdecoder 120 through a plurality of word lines WLs, a drain select lineDSL, and a source select line SSL. The memory blocks BLK1 to BLKz arecoupled to the read-and-write circuit 130 through bit lines BL1 to BLm.Each of the memory blocks BLK1 to BLKz includes a plurality of memorycells. In an embodiment, the memory cells are nonvolatile memory cells,and in particular, the memory cells may be charge trap device-basednonvolatile memory cells. Memory cells coupled to the same word lineamong the plurality of memory cells are defined as one page. In otherwords, the memory cell array 110 is formed of a plurality of pages. Eachof the memory blocks BLK1 to BLKz of the memory cell array 110 includesa plurality of memory strings. Each of the memory strings includes adrain select transistor, a plurality of memory cells, and a sourceselect transistor which are coupled in series between a correspondingbit line and a source line.

The address decoder 120, the read-and-write circuit 130, and the voltagegenerator 150 may function as peripheral circuits for driving the memorycell array 110.

The address decoder 120 is coupled to the memory cell array 110 throughthe plurality of word lines WLs, the drain select line DSL, and thesource select line SSL. The address decoder 120 is configured to beoperated under control signals AD_signals outputted from the controllogic 140. The address decoder 120 receives an address ADDR through aninput/output buffer (not illustrated) provided in the semiconductormemory device 100.

The address decoder 120 applies a program voltage Vpgm, a plurality ofpass voltages Vpass1, Vpass2, and Vpass3, a verification voltageVverify, a drain control voltage VDSL, and a source control voltageVSSL, which are generated from the voltage generator 150, to the wordlines WLs, the drain select line DSL, and the source select SSL of thememory cell array 110.

A program operation of the semiconductor memory device 100 is performedin pages. Addresses ADDR received in a request for the program operationinclude a block address, a row address, and a column address. Theaddress decoder 120 selects a corresponding one of the memory blocks anda corresponding one of the word lines in accordance with the blockaddress and the row address. The column address Yi is decoded by theaddress decoder 120 and provided to the read-and-write circuit 130.

The address decoder 120 may include a block decoder, a row decoder, acolumn decoder, an address buffer, etc.

The read-and-write circuit 130 includes a plurality of page buffers PB1to PBm. The page buffers PB1 to PBm are coupled to the memory cell array110 through bit lines BL1 to BLm. Each of the page buffers PB1 to PBmtemporarily stores data DATA inputted during the program operation andcontrols the potential of a corresponding one of the bit lines BL1 toBLm in accordance with the temporarily stored data. Each of the pagebuffers PB1 to PBm senses current and voltage of a corresponding one ofthe bit lines BL1 to BLm while performing a verification operation ofthe program operation.

The read-and-write circuit 130 is operated under control signalsPB_signals outputted from the control logic 140.

The control logic 140 is coupled to the address decoder 120, theread-and-write circuit 130, and the voltage generator 150. The controllogic 140 receives a command CMD through the input/output buffer (notillustrated) provided in the semiconductor memory device 100. Thecontrol logic 140 is configured to control the overall operation of thesemiconductor memory device 100 in response to the command CMD.

The control logic 140 may control the voltage generator 150 and theaddress decoder 120 so that during the program operation, electrons aredispersed and trapped in a trap layer between the memory cells. Thiswill be explained below in the accompanying description of a method ofoperating the semiconductor memory device.

The voltage generator 150 is operated under control signals VG_signalsoutputted from the control logic 140.

The voltage generator 150 generates a program voltage Vpgm to be appliedto a selected word line, first and second pass voltages Vpass1 and pass2to be applied to non-selected word lines, a verification voltage Vverifyto be applied to the selected word line during a verification operation,and a third pass voltage Vpass3 to be applied to the non-selected wordlines during the verification operation. The potential level of thesecond pass voltage Vpass1 may be higher than that of the first passvoltage Vpass1.

FIG. 2 is a block diagram illustrating a representation of an example ofan embodiment of the memory cell array 110 of FIG. 1.

Referring to FIG. 2, the memory cell array 110 may include the pluralityof memory blocks BLK1 to BLKz. Each memory block has a three-dimensionalstructure. Each memory block includes a plurality of memory cellsstacked on a substrate. The memory cells are arranged in +X, +Y, and +zdirections. The structure of each memory block will be described laterherein with reference to FIGS. 3 and 4.

FIG. 3 is a three-dimensional view illustrating a representation of anexample of a memory string included in each memory block according tothe present disclosure. FIG. 4 is a circuit diagram illustrating arepresentation of an example of the memory string.

Referring to FIGS. 3 and 4, a source line SL is formed on asemiconductor substrate. A vertical channel layer SP is formed on thesource line SL. An upper portion of the vertical channel layer SP iscoupled to a corresponding bit line BL. The vertical channel layer SPmay be made of polysilicon. A plurality of conductive layers SSL, WL0 toWLn, and DSL are formed at different heights on the vertical channellayer SP in such a way each of the conductive layers encloses thevertical channel layer SP. A multilayer film (not illustrated) includinga charge storage layer is formed on a surface of the vertical channellayer SP. The multilayer film is also disposed between the verticalchannel layer SP and the conductive layers SSL, WL0 to WLn, and DSL. Themultilayer film may be formed in an ONO structure in which an oxidelayer, a nitride layer, and an oxide layer are successively stacked.

The lowermost conductive layer forms a source select line SSL. Theuppermost conductive layer forms a drain select line DSL. The conductivelayers disposed between the select lines SSL and DSL form the respectiveword lines WL0 to WLn. In other words, the conductive layers SSL, WL0 toWLn, and DSL are formed in a multilayer structure on the semiconductorsubstrate. The vertical channel SP passing through the conductive layersSSL, WL0 to WLn, and DSL is vertically coupled between the bit line BLand the source line SL formed on the semiconductor substrate.

The drain select transistor DST is formed on a portion of the uppermostconductive layer DSL that encloses the vertical channel layer SP. Thesource select transistor SST is formed on a portion of the lowermostconductive layer SSL that encloses the vertical channel layer SP. Memorycells C0 to Cn are formed on portions of the intermediate conductivelayers WL0 to WLn that enclose the vertical channel layer SP.

The memory string may include the source select transistor SST, thememory cells C0 to Cn, and the drain select transistor DST, which arevertically coupled to the substrate between the source line SL and thebit line BL. The source select transistor SST electrically connects thememory cells C0 to Cn to the source line SL depending on a sourcecontrol voltage applied to the source select line SSL. The drain selecttransistor DST electrically connects the memory cells C0 to Cn to thebit line BL depending on a drain control voltage applied to the drainselect line DSL.

FIG. 5 is a flowchart illustrating a representation of an example of theoperation of the semiconductor memory device according to an embodimentof the present disclosure.

FIG. 6 is a waveform diagram representation of examples of signalsapplied to the memory cell array when the semiconductor memory device isoperated according to an embodiment of the present disclosure.

FIGS. 7A to 7D are diagrams illustrating representations of examples ofthe movement of electric charges trapped in a memory layer of a memorycell during a program operation of the semiconductor memory deviceaccording to an embodiment of the present disclosure.

A method of operating the semiconductor memory device according to anembodiment of the present disclosure will be described with reference toFIGS. 1 to 7D.

1) Applying a Program Voltage (S110; Section A)

When a command CMD for performing a program operation of thesemiconductor memory device is transmitted to the control logic 140, thecontrol logic 140 outputs control signals PB_signals. In response to thecontrol signals PB_signals outputted from the control logic 140, theread-and-write circuit 130 temporarily stores data DATA to beprogrammed, inputted from the outside, in the plurality of page buffersPB1 to PBm. Each of the page buffers PB1 to PBm temporarily stores dataDATA inputted during the program operation and controls the potential ofa corresponding one of the bit lines BL1 to BLm in accordance with thetemporarily stored data.

The voltage generator 150 generates a program voltage Vpgm and a firstpass voltage Vpass1 in response to control signals VG_signals outputtedfrom the control logic 140. In response to an address ADDR and controlsignals AD_signals outputted from the control logic 140, the addressdecoder 120 applies the program voltage Vpgm to a selected word line(e.g., WL1) of the word lines WLs and applies the first pass voltageVpass1 to the other unselected word lines (e.g., WL0 and WL2).

As illustrated in FIG. 7A, electric charges ( ) are drawn from thevertical channel layer SP into the memory layer ML of the selectedmemory cell coupled to the selected word line WL1 and are trapped in thememory layer ML. Thereby, the threshold voltage of the selected memorycell is increased.

2) Discharging the Program Voltage and Maintaining the Pass Voltage ofthe Adjacent Word Lines (S120; Section B)

After section A, the voltage generator 150 discharges the potentiallevel of the program voltage Vpgm that has been applied to the selectedword line (e.g., WL1) to a voltage of 0V. The voltage generator 150continuously applies the first pass voltage Vpass1 to the word lines(e.g., WL0 and WL2) adjacent to the selected word line (e.g., WL1) orapplies a second pass voltage Vpass2 higher in potential level than thefirst pass voltage Vpass1 to the adjacent word lines (WL0 and WL2).

Referring to FIG. 7B, an electric field is formed by the first passvoltage Vpass1 or the second pass voltage Vpass2 applied to the wordlines WL0 and WL2 adjacent to the selected word line WL1, so that someof the electric charges ( ) trapped in the memory layer ML of theselected cell move in both side directions. That is, some of theelectric charges ( ) move to portions of the memory layer ML that aredefined between the selected memory cell and the adjacent memory cells.

3) Discharging the Pass Voltage (S130; Section C)

After section B, the voltage generator 150 discharges the potentiallevel of the first pass voltage Vpass1 or the second pass voltage Vpass2that has been applied to the adjacent word lines WL0 and WL2 to avoltage of 0V.

Referring to FIG. 7C, the electric charges ( ) that have moved to theportions of the memory layer ML defined between the selected memory celland the adjacent memory cells and the electric charges ( ) trapped inthe memory layer ML of the selected memory cell are rearranged.Therefore, a short-time retention characteristic, in which electriccharges ( ) move to adjacent regions within a short time after havingbeen trapped in the memory layer ML and thus the threshold voltagereduces, is reflected in the threshold voltage of the selected memorycell.

4) Applying a Verification Voltage and a Pass Voltage (S140; Section D)

After section C, the voltage generator 150 generates a verificationvoltage Vverify and a third pass voltage Vpass3 in response to controlsignals VG_signals outputted from the control logic 140. In response toan address ADDR and control signals AD_signals outputted from thecontrol logic 140, the address decoder 120 applies the verificationvoltage Vverify to the selected word line (e.g., WL1) of the word linesWLs and applies the third pass voltage Vpass3 to the other unselectedword lines (e.g., WL0 and WL2).

Each of the page buffers PB1 to PBm of the read-and-write circuit 130senses, in response to control signals PB_signals outputted from thecontrol logic 140, the potential level or current of the correspondingone of the bit lines BL1 to BLm and thus performs a verificationoperation.

5) Floating the Word Lines (S150; Section E)

After section D, the voltage generator 150 discharges the verificationvoltage Vverify applied to the selected word line (e.g., WL1) and thethird voltage Vpass3 to a voltage of 0V. The address decoder 120 floatsthe word lines WLs such that the word lines WLs are in an idle state.

After the word line floating step S150 has been performed, when theresult of the verification operation is determined as fail, the programvoltage Vpgm is increased by a step voltage, and the operation of thesemiconductor memory device is re-performed from the above-mentionedprogram voltage application step S110. When the result of theverification operation is determined as pass, a program operation formemory cells of a subsequent page may be performed.

According to an above-mentioned embodiment of the present disclosure,the verification operation is performed, after the electric chargestrapped after the program voltage is applied have been rearranged bymoving some of the electric charges in both side directions of theselected memory cell and the short-time retention characteristic hasbeen reflected. Therefore, a problem of the threshold voltagedistribution being reduced after the verification operation has beenperformed can be mitigated.

FIG. 8 is a flowchart illustrating a representation of an example of theoperation of a semiconductor memory device according to an embodiment ofthe present disclosure.

FIG. 9 is a waveform diagram representation of examples of signalsapplied to the memory cell array when the semiconductor memory device isoperated according to an embodiment of the present disclosure.

FIGS. 10A to 10D are diagrams illustrating representations of examplesof the movement of electric charges trapped in a memory layer of amemory cell during a program operation of the semiconductor memorydevice according to an embodiment of the present disclosure.

A method of operating the semiconductor memory device according to anembodiment of the present disclosure will be described with reference toFIGS. 1 to 4 and 8 to 10D.

1) Applying a Program Voltage (S210; Section A)

When a command CMD for performing a program operation of thesemiconductor memory device is transmitted to the control logic 140, thecontrol logic 140 outputs control signals PB_signals. In response to thecontrol signals PB_signals outputted from the control logic 140, theread-and-write circuit 130 temporarily stores data DATA to beprogrammed, inputted from the outside, in the plurality of page buffersPB1 to PBm. Each of the page buffers PB1 to PBm temporarily stores dataDATA inputted during the program operation and controls the potential ofa corresponding one of the bit lines BL1 to BLm in accordance with thetemporarily stored data.

The voltage generator 150 generates a program voltage Vpgm, a first passvoltage Vpass1, and a drain control voltage VDSL in response to controlsignals VG_signals outputted from the control logic 140. In response toan address ADDR and control signals AD_signals outputted from thecontrol logic 140, the address decoder 120 applies the program voltageVpgm to a selected word line (e.g., WL1) of the word lines WLs, appliesthe first pass voltage Vpass1 to the other unselected word lines (e.g.,WL0 and WL2), and applies the drain control voltage VDSL to the drainselect line DSL.

As illustrated in FIG. 10A, electric charges ( ) are drawn from thevertical channel layer SP into the memory layer ML of the selectedmemory cell coupled to the selected word line WL1 and are trapped in thememory layer ML. Thereby, the threshold voltage of the selected memorycell is increased.

2) Discharging the Program Voltage and the Drain Control Voltage, andMaintaining the Pass Voltage of the Adjacent Word Lines (S220; SectionB)

After section A, the voltage generator 150 discharges the potentiallevel of the program voltage Vpgm that has been applied to the selectedword line (e.g., WL1) to a voltage of 0V. The voltage generator 150continuously applies the first pass voltage Vpass1 to the word lines(e.g., WL0 and WL2) adjacent to the selected word line (e.g., WL1) orapplies a second pass voltage Vpass2 higher in potential level than thefirst pass voltage Vpass1 to the adjacent word lines (WL0 and WL2). Thevoltage generator 150 discharges the potential level of the draincontrol voltage VDSL applied to the drain select line DSL to a voltageof 0V. Thereby, the drain select transistor DST is turned off, wherebythe vertical channel layer SP of the memory string is electricallyseparated from the corresponding bit line and thus enters a floatingstate. In this case, the source select transistor SST is in a turned-offstate. Therefore, portions of the vertical channel layer that are closeto the adjacent memory cells to which the first pass voltage Vpass1 orthe second pass voltage Vpass2 are applied are boosted to a highpotential level, and the selected memory cell to which a voltage of 0Vis applied is boosted to a relatively low potential level.

Thereby, as illustrated in FIG. 10B, an electric field is formed both bythe first pass voltage Vpass1 or the second pass voltage Vpass2 appliedto the word lines WL0 and WL2 adjacent to the selected word line WL1 andby the boosted potential of the portions of the vertical channel layerthat are close to the word lines WL0 and WL2, so that some of theelectric charges ( ) trapped in the memory layer ML of the selected cellmove in both side directions. That is, some of the electric charges ( )move to portions of the memory layer ML that are defined between theselected memory cell and the adjacent memory cells.

3) Discharging the Pass Voltage (S230; Section C)

After section B, the voltage generator 150 discharges the potentiallevel of the first pass voltage Vpass1 or the second pass voltage Vpass2that has been applied to the adjacent word lines WL0 and WL2 to avoltage of 0V.

Thereby, as illustrated in FIG. 10C, the electric charges ( ) that havemoved to the portions of the memory layer ML defined between theselected memory cell and the adjacent memory cells and the electriccharges ( ) trapped in the memory layer ML of the selected memory cellare rearranged. Therefore, the short-time retention characteristic isreflected in the threshold voltage of the selected memory cell.

4) Applying a Verification Voltage and a Pass Voltage (S240; Section D)

After section C, the voltage generator 150 generates a verificationvoltage Vverify, a third pass voltage Vpass3, and a drain controlvoltage VDSL in response to control signals VG_signals outputted fromthe control logic 140. In response to an address ADDR and controlsignals AD_signals outputted from the control logic 140, the addressdecoder 120 applies the verification voltage Vverify to the selectedword line (e.g., WL1) of the word lines WLs, applies the third passvoltage Vpass3 to the other unselected word lines (e.g., WL0 and WL2),and applies the drain control voltage VDSL to the drain select line DSL.

Each of the page buffers PB1 to PBm of the read-and-write circuit 130senses, in response to control signals PB_signals outputted from thecontrol logic 140, the potential level or current of the correspondingone of the bit lines BL1 to BLm and thus performs a verificationoperation.

5) Floating the Word Lines (S250)

After section D, the voltage generator 150 discharges the verificationvoltage Vverify applied to the selected word line (e.g., WL1), the thirdvoltage Vpass3, and the drain control voltage VDSL to a voltage of 0V.The address decoder 120 floats the word lines WLs such that the wordlines WLs are in an idle state.

After the word line floating step S250 has been performed, when theresult of the verification operation is determined as fail, the programvoltage Vpgm is increased by a step voltage, and the operation of thesemiconductor memory device is re-performed from the above-mentionedprogram voltage application step S210. When the result of theverification operation is determined as pass, a program operation formemory cells of a subsequent page may be performed.

According to an above-mentioned embodiment of the present disclosure,the verification operation is performed, after the electric chargestrapped after the program voltage is applied have been rearranged bymoving some of the electric charges in both side directions of theselected memory cell and the short-time retention characteristic hasbeen reflected. Therefore, a problem of the threshold voltagedistribution being reduced after the verification operation has beenperformed can be mitigated.

FIG. 11 is a flowchart illustrating a representation of an example ofthe operation of a semiconductor memory device according to anembodiment of the present disclosure.

FIGS. 12A and 12B are waveform diagram representations of examples ofsignals applied to the memory cell array when the semiconductor memorydevice is operated according to an embodiment of the present disclosure.

FIGS. 13A to 13D are diagrams illustrating representations of examplesof the movement of electric charges trapped in a memory layer of amemory cell during the operation of the semiconductor memory deviceaccording to an embodiment of the present disclosure.

A method of operating the semiconductor memory device according to anembodiment of the present disclosure will be described with reference toFIGS. 1 to 4 and 11 to 13D.

The method of operating the semiconductor memory device according to anembodiment of the present disclosure is preferably performed before theprogram operation.

1) Applying a Program Voltage to Even Word Lines, and Applying a PassVoltage to Odd Word Lines (S310)

The read-and-write circuit 130 sets the potentials of the bit lines BL1to BLm of the memory cell array 110 to a program allowable level (e.g.,0V) in response to control signals PB_signals outputted from the controllogic 140.

The voltage generator 150 generates a program voltage Vpgm, a first passvoltage Vpass1, and a drain control voltage VDSL in response to thecontrol signals VG_signals outputted from the control logic 140. Inresponse to an address ADDR and control signals AD_signals outputtedfrom the control logic 140, the address decoder 120 applies the programvoltage Vpgm to even word lines (WL0, WL2, . . . ) of the word linesWLs, applies the first pass voltage Vpass1 to odd word lines (WL1, WL3,. . . ), and applies a drain control voltage VDSL to the drain selectline DSL.

Referring to FIG. 13A, electric charges ( ) are drawn from the verticalchannel layer SP into the memory layer ML of the even memory cellscoupled to the even word lines WL0, WL2, . . . and are trapped in thememory layer ML. Therefore, the threshold voltage of the even memorycells is increased.

2) Discharging the Even Word Lines, and Applying the Program Voltage tothe Odd Word Lines (S320)

In response to control signals VG_signals outputted from the controllogic 140, the voltage generator 150 discharges the program voltage Vpgmthat has been applied to the even word lines WL0, WL2, . . . to avoltage of 0V and applies the program voltage Vpgm to the odd word linesWL1, WL3, . . . to which the first pass voltage Vpass1 has been applied.The voltage generator 150 discharges the drain control voltage VDSL thathas been applied to the drain select line DSL to a voltage of 0V.Thereby, the drain select transistor DST is turned off, whereby thevertical channel layer SP of the memory string is electrically separatedfrom the corresponding bit line and thus enters a floating state. Inthis case, the source select transistor SST is in a turned-off state.

Therefore, as illustrated in FIG. 13B, portions of the vertical channellayer that are close to the odd memory cells coupled to the odd wordlines to which the program voltage Vpgm is applied are boosted to a highpotential level, and the even memory cells to which a voltage of 0V isapplied are boosted to a relatively low potential level. Thereby, anelectric field is formed by the program voltage Vpgm and the boostedpotential of the portions of the vertical channel layer that are closeto the odd word lines, so that some of the electric charges ( ) trappedin the memory layer ML of each even memory cell move in both sidedirections.

3) Erase Operation (S330)

After step S320, an erase operation is conducted to detrap the electriccharges ( ) that have been trapped in the memory layer ML of the evenmemory cells. The erase operation is performed such that the electriccharges ( ) that have moved in both side directions of each even memorycell remain. The erase operation may be performed by applying an erasevoltage generated from the voltage generator 150 to the source lie SL ofthe memory cell array 110.

The erase operation S330 may be skipped before a subsequent step S340 isperformed.

4) Applying a Program Voltage to the Odd Word Lines, and Applying a PassVoltage to the Odd Word Lines (S340)

The voltage generator 150 generates a program voltage Vpgm, a first passvoltage Vpass1, and a drain control voltage VDSL in response to thecontrol signals VG_signals outputted from the control logic 140. Inresponse to an address ADDR and control signals AD_signals outputtedfrom the control logic 140, the address decoder 120 applies the programvoltage Vpgm to the odd word lines (WL1, WL3, . . . ) of the word linesWLs, applies the first pass voltage Vpass1 to the even word lines (WL0,WL2, . . . ), and applies the drain control voltage VDSL to the drainselect line DSL.

Referring to FIG. 13C, electric charges ( ) are drawn from the verticalchannel layer SP into the memory layer ML of the odd memory cellscoupled to the odd word lines WL1, WL3, . . . and are trapped in thememory layer ML. Therefore, the threshold voltage of the even memorycells is increased. Furthermore, electric charges ( ) that have beenmoved at step S320 remain on opposite sides of each of the memory cells.

5) Discharging the Odd Word Lines, and Applying the Program Voltage tothe Even Word Lines (S350)

In response to control signals VG_signals outputted from the controllogic 140, the voltage generator 150 discharges the program voltage Vpgmthat has been applied to the odd word lines WL1, WL3, . . . to a voltageof 0V and applies the program voltage Vpgm to the even word lines WL0,WL2, . . . to which the first pass voltage Vpass1 has been applied.

The voltage generator 150 discharges the drain control voltage VDSL thathas been applied to the drain select line DSL to a voltage of 0V.Thereby, the drain select transistor DST is turned off, whereby thevertical channel layer SP of the memory string is electrically separatedfrom the corresponding bit line and thus enters a floating state. Inthis case, the source select transistor SST is in a turned-off state.

Therefore, referring to FIG. 13D, portions of the vertical channel layerthat are close to the even memory cells coupled to the even word linesto which the program voltage Vpgm is applied are boosted to a highpotential level, and the odd memory cells to which a voltage of 0V isapplied are boosted to a relatively low potential level. Thereby, anelectric field is formed by the program voltage Vpgm and the boostedpotential of the portions of the vertical channel layer that are closeto the even word lines, so that some of the electric charges ( ) trappedin the memory layer ML of each odd memory cell move in both sidedirections.

6) Erase Operation (S360)

After step S350, an erase operation is conducted to detrap the electriccharges ( ) that have been trapped in the memory layer ML of the oddmemory cells. The erase operation may be performed by applying an erasevoltage generated from the voltage generator 150 to the source lie SL ofthe memory cell array 110. If the above-mentioned erase operation S330is skipped, erase operations of the even memory cells and the odd memorycells are performed together at step S360. Preferably, the eraseoperation is performed such that the electric charges A and B that havebeen moved in both side directions of the corresponding memory cellsremain.

Subsequently, the program operation may be performed.

According to an embodiment of the present disclosure, before the programoperation is performed, electric charges can be trapped in advance inthe memory layer between the memory cells so as to increase the densityof charges. Therefore, during a subsequent program operation, aphenomenon in which electric charges trapped in the memory layer of eachmemory cell move in both side directions is restricted, whereby aproblem of variation in threshold voltage can be mitigated.

FIG. 14 is a flowchart illustrating a representation of an example ofthe operation of a semiconductor memory device according to anembodiment of the present disclosure.

FIG. 15 is a waveform diagram representation of examples of signalsapplied to a memory cell array when the semiconductor memory device isoperated according to an embodiment of the present disclosure.

FIGS. 16A to 16D are diagrams illustrating representations of examplesof the movement of electric charges trapped in a memory layer of amemory cell during a program operation of the semiconductor memorydevice according to an embodiment of the present disclosure.

The method of operating the semiconductor memory device according to anembodiment of the present disclosure will be described with reference toFIGS. 1 to 4 and 14 to 16D.

The method of operating the semiconductor memory device according to anembodiment of the present disclosure is included in the erase operationof the semiconductor memory device and, in particular, preferablyperformed before an erase voltage application operation of the eraseoperation of the semiconductor memory device.

Furthermore, the method of operating the semiconductor memory deviceaccording to an embodiment of the present disclosure may be performedbefore the program operation.

1) Applying a Program Voltage to all of the Word Lines (S410)

The read-and-write circuit 130 sets the potentials of the bit lines BL1to BLm of the memory cell array 110 to a program allowable level (e.g.,0V) in response to control signals PB_signals outputted from the controllogic 140.

The voltage generator 150 generates a program voltage Vpgm and a draincontrol voltage VDSL in response to control signals VG_signals outputtedfrom the control logic 140. In response to control signals AD_signalsoutputted from the control logic 140, the address decoder 120 appliesthe program voltage Vpgm to the word lines WLs and applies the draincontrol voltage VDSL to the drain select line DSL.

Referring to FIG. 16A, electric charges ( ) are drawn from the verticalchannel layer SP into the memory layer ML of all of the memory cellscoupled to the respective word lines (WLs; WL0, WL2, WL3, . . . ) andare trapped in the memory layer ML. Some electric charges ( ) may betrapped in the memory layer ML between the memory cells by the programvoltage Vpgm applied to all of the word lines WLs.

2) Discharging the Even Word Lines, and Discharging the Drain ControlVoltage (S420)

The voltage generator 150 discharges, in response to control signalsVG_signals outputted from the control logic 140, the potential level ofthe program voltage Vpgm that has been applied to the even word lines(WL0, WL2, . . . ). For example, the program voltage Vpgm that has beento the even word lines WL0, WL2, . . . may be discharged to a voltage of0V. The voltage generator 150 retains the potential level of the programvoltage Vpgm applied to the odd word lines (WL1, WL3, . . . ). Thevoltage generator 150 discharges the drain control voltage VDSL that hasbeen applied to the drain select line DSL to a voltage of 0V.

Therefore, referring to FIG. 16B, portions of the vertical channel layerthat correspond to the odd memory cells coupled to the odd word lines towhich the program voltage Vpgm is applied are boosted to a highpotential level, and the even memory cells coupled to the even wordlines from which the program voltage Vpgm has been discharged areboosted to a relatively low potential level. Thereby, an electric fieldis formed by the program voltage Vpgm and the boosted potential of theportions of the vertical channel layer that are close to the odd wordlines, so that some of the electric charges ( ) trapped in the memorylayer ML of each even memory cell move in both side directions.

3) Applying a Program Voltage to the Even Word Lines, and Dischargingthe Odd Word Lines (S430)

The voltage generator 150 discharges, in response to control signalsVG_signals outputted from the control logic 140, the potential level ofthe program voltage Vpgm that has been applied to the odd word lines(WL1, WL3, . . . ). For example, the program voltage Vpgm that has beento the odd word lines WL1, WL3, . . . may be discharged to a voltage of0V. The voltage generator 150 applies a program voltage Vpgm to the evenword lines (WL0, WL2, . . . ).

Therefore, referring to FIG. 16C, portions of the vertical channel layerthat correspond to the even memory cells coupled to the even word linesto which the program voltage Vpgm is applied are boosted to a highpotential level, and the odd memory cells coupled to the odd word linesfrom which the program voltage Vpgm has been discharged are boosted to arelatively low potential level. Thereby, an electric field is formed bythe program voltage Vpgm and the boosted potential of the portions ofthe vertical channel layer that are close to the even word lines, sothat some of the electric charges ( ) trapped in the memory layer ML ofeach odd memory cell move in both side directions.

4) Erase Operation (S440)

An erase operation is performed to detrap the electric charges ( ) thathave been trapped in the memory layer ML of the even memory cells andthe even memory cells. The erase operation is performed such that theelectric charges ( ) that are trapped in the memory layer between theeven memory cells and the odd memory cells remain. The erase operationmay be performed by applying an erase voltage generated from the voltagegenerator 150 to the source lie of the memory cell array 100.

Subsequently, the program operation may be performed.

According to the present embodiment of the present disclosure, beforethe program operation is performed, electric charges can be trapped inadvance in the memory layer between the memory cells so as to increasethe density of charges. Therefore, during a subsequent programoperation, a phenomenon in which electric charges trapped in the memorylayer of the memory cells move in both side directions is restricted,whereby a problem of variation in threshold voltage can be mitigated.

FIG. 17 is a block diagram illustrating a representation of an exampleof a memory system including the semiconductor memory device of FIG. 1.

Referring FIG. 17, the memory system 1000 may include a semiconductormemory device 100 and a controller 1100.

The semiconductor memory device 100 may have the same configuration andoperation as those of the semiconductor memory device described withreference to FIG. 1. Hereinafter, repetitive explanations will beomitted.

The controller 1100 is coupled to a host and the semiconductor memorydevice 100. In response to a request from the host, the controller 1100accesses the semiconductor memory device 100. For example, thecontroller 1100 controls read, write, erase, and background operationsof the semiconductor memory device 100. The controller 1100 isconfigured to provide an interface between the host and thesemiconductor memory device 100. The controller 1100 is configured todrive firmware for controlling the semiconductor memory device 100.

The controller 1100 includes a RAM (random access memory) 1110, aprocessing unit 1120, a host interface 1130, a memory interface 1140,and an error correction block 1150. The RAM 1110 is used as at least oneof an operation memory of the processing unit 1120, a cache memorybetween the semiconductor memory device 100 and the host, and a buffermemory between the semiconductor memory device 100 and the host. Theprocessing unit 1120 controls the overall operation of the controller1100. In addition, the controller 1100 may temporarily store programdata provided from the host during the write operation.

The host interface 1130 includes a protocol for performing data exchangebetween the host and the controller 1100. In an exemplary embodiment,the controller 1200 is configured to communicate with the host throughat least one of various interface protocols such as a universal serialbus (USB) protocol, a multimedia card (MMC) protocol, a peripheralcomponent interconnection (PCI) protocol, a PCI-express (PCI-E)protocol, an advanced technology attachment (ATA) protocol, a serial-ATAprotocol, a parallel-ATA protocol, a small computer small interface(SCSI) protocol, an enhanced small disk interface (ESDI) protocol, andan integrated drive electronics (IDE) protocol, a private protocol, andthe like.

The memory interface 1140 interfaces with the semiconductor memorydevice 100. For example, the memory interface includes a NAND interfaceor NOR interface.

The error correction block 1150 uses an error correction code (ECC) todetect and correct an error in data received from the semiconductormemory device 100. The processing unit 1120 may adjust the read voltageaccording to an error detection result from the error correction block1150, and control the semiconductor memory device 100 to performre-reading. In an exemplary embodiment, the error correction block maybe provided as an element of the controller 1100.

The controller 1100 and the semiconductor memory device 100 may beintegrated into a single semiconductor device. In an exemplaryembodiment, the controller 1100 and the semiconductor memory device 100may be integrated into a single semiconductor device to form a memorycard. For example, the controller 1100 and the semiconductor memorydevice 100 may be integrated into a single semiconductor device and forma memory card such as a personal computer memory card internationalassociation (PCMCIA), a compact flash card (CF), a smart media card (SMor SMC), a memory stick multimedia card (MMC, RS-MMC, or MMCmicro), a SDcard (SD, miniSD, microSD, or SDHC), a universal flash storage (UFS),and the like.

The controller 1100 and the semiconductor memory device 100 may beintegrated into a single semiconductor device to form a solid statedrive (SSD). The SSD includes a storage device formed to store data in asemiconductor memory. When the memory system 1000 is used as the SSD, anoperation speed of the host coupled to the memory system 2000 may bephenomenally improved.

In an embodiment, the memory system 1000 may be provided as one ofvarious elements of an electronic device such as a computer, a ultramobile PC (UMPC), a workstation, a net-book, a personal digitalassistants (PDA), a portable computer, a web tablet, a wireless phone, amobile phone, a smart phone, an e-book, a portable multimedia player(PMP), a game console, a navigation device, a black box, a digitalcamera, a 3-dimensional television, a digital audio recorder, a digitalaudio player, a digital picture recorder, a digital picture player, adigital video recorder, a digital video player, a device capable oftransmitting/receiving information in an wireless environment, one ofvarious devices for forming a home network, one of various electronicdevices for forming a computer network, one of various electronicdevices for forming a telematics network, an RFID device, one of variouselements for forming a computing system, or the like.

In an example of an embodiment, the semiconductor memory device 100 orthe memory system 1000 may be embedded in various types of packages. Forexample, the semiconductor memory device 100 or the memory system 1000may be packaged in a type such as Package on Package (PoP), Ball gridarrays (BGAs), Chip scale packages (CSPs), Plastic Leaded Chip Carrier(PLCC), Plastic Dual In Line Package (PDIP), Die in Waffle Pack, Die inWafer Form, Chip On Board (COB), Ceramic Dual In Line Package (CERDIP),Plastic Metric Quad Flat Pack (MQFP), Thin Quad Flatpack (TQFP), SmallOutline (SOIC), Shrink Small Outline Package (SSOP), Thin Small Outline(TSOP), Thin Quad Flatpack (TQFP), System In Package (SIP), Multi ChipPackage (MCP), Wafer-level Fabricated Package (WFP), Wafer-LevelProcessed Stack Package (WSP), or the like.

FIG. 18 is a block diagram illustrating a representation of an exampleof an application example of the memory system of FIG. 17.

Referring FIG. 18, the memory system 2000 may include a semiconductormemory device 2100 and a controller 2200. The semiconductor memorydevice 2100 includes a plurality of memory chips. The semiconductormemory chips are divided into a plurality of groups.

Referring to FIG. 18, it is illustrated that each of the plurality ofgroups communicates with the controller 2200 through first to k-thchannels CH1 to CHk. Each semiconductor memory chip is configured tooperate in the same manner as that of an embodiment of the semiconductormemory device 100 described with reference to FIG. 1.

Each group communicates with the controller 2200 through one commonchannel. The controller 2200 has the same configuration as that of thecontroller 1100 described with reference to FIG. 17 and is configured tocontrol a plurality of memory chips of the semiconductor memory device2100 through the plurality of channels CH1 to CHk.

FIG. 19 is a block diagram illustrating a representation of an exampleof a computing system including the memory system illustrated withreference to FIG. 18.

Referring to FIG. 19, the computing system 3000 may include a centralprocessing unit 3100, a RAM 3200, a user interface 3300, a power supply3400, a system bus 3500, and a memory system 2000.

The memory system 2000 is electrically connected to the CPU 3100, theRAM 3200, the user interface 3300, and the power supply 3400 through thesystem bus 3500. Data provided through the user interface 3300 orprocessed by the CPU 3100 is stored in the memory system 2000.

Referring to FIG. 19, the semiconductor memory device 2100 isillustrated as being coupled to the system bus 3500 through thecontroller 2200. However, the semiconductor memory device 2100 may bedirectly coupled to the system bus 3500. The function of the controller2200 may be performed by the CPU 3100 and the RAM 3200.

Referring to FIG. 19, the memory system 2000 described with reference toFIG. 18 is illustrated as being used. However, the memory system 2000may be replaced with the memory system 1000 described with reference toFIG. 17. In an embodiment, the computing system 3000 may include all ofthe memory systems 1000 and 2000 described with reference to FIGS. 17and 18. Various embodiments of the present disclosure can overcomeretention deterioration characteristics of a semiconductor memorydevice, thus solving a problem of a reduction in threshold voltage ofmemory cells due to retention deterioration characteristics.

Examples of embodiments have been disclosed herein, and althoughspecific terms are employed, they are used and are to be interpreted ina generic and descriptive sense only and not for the purpose oflimitation. In some instances, as would be apparent to one of ordinaryskill in the art as of the filing of the present application, features,characteristics, and/or elements described in connection with aparticular embodiment may be used singly or in combination withfeatures, characteristics, and/or elements described in connection withother embodiments unless otherwise specifically indicated. Accordingly,it will be understood by those of skill in the art that various changesin form and details may be made without departing from the spirit andscope of the present disclosure as set forth in the following claims.

What is claimed is:
 1. A semiconductor memory device, comprising: amemory cell array including a drain select transistor and a plurality ofmemory cells; a voltage generator configured to apply a program voltage,and first and second pass voltages to the memory cell array; and acontrol logic configured to control the voltage generator to apply theprogram voltage to a selected memory cell of the plurality of memorycells during a program operation, apply the first pass voltage toremaining non-selected memory cells, and apply the second pass voltagehigher than the first pass voltage to memory cells adjacent to theselected memory cell of the non-selected memory cells after completingdischarging the program voltage applied to the selected memory cell. 2.The semiconductor memory device according to claim 1, wherein thecontrol logic controls the voltage generator so that the program voltageapplied to the selected memory cell is discharged to a voltage of 0V. 3.The semiconductor memory device according to claim 1, wherein thevoltage generator is configured to apply a drain control voltage to thememory cell array, and wherein the control logic controls the voltagegenerator so that: when the program voltage is applied to the selectedmemory cell, the drain control voltage is applied to the drain selecttransistor of the memory cell array; and when the program voltageapplied to the selected memory cell is discharged, the drain controlvoltage is discharged so that the drain select transistor is turned off.4. The semiconductor memory device according to claim 1, wherein thecontrol logic controls the voltage generator so that the second passvoltage applied to the memory cells adjacent to the selected memory cellis discharged after a predetermined period of time has passed after theprogram voltage has been discharged.
 5. The semiconductor memory deviceaccording to claim 4, wherein the control logic controls the voltagegenerator so that a verification voltage is applied to the selectedmemory cell after the second pass voltage applied to the memory cellsadjacent to the selected memory cell is discharged.
 6. The semiconductormemory device according to claim 5, wherein the voltage generatorapplies the verification voltage to the selected memory cell, and thenfloats word lines of the memory cell array.
 7. The semiconductor memorydevice according to claim 5, wherein when the voltage generator appliesthe verification voltage to the selected memory cell the voltagegenerator applies a third pass voltage to the memory cells adjacent tothe selected memory cell.